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Extragalactic

Having ISO in space gave astronomers special opportunities to study the history of galaxies.

Evolving galaxies

Having ISO in space gave astronomers special opportunities to study the history of galaxies. By detecting infrared wavelengths that are hard to observe from the Earth, ISO has picked out very clearly the galaxies that are evolving most rapidly via periods of intensive starmaking. ISO has also detected infrared galaxies powered by active galactic nuclei.

ISO has observed many galaxies which are half as old as the Universe by staring through a window in the dust of our own Milky Way Galaxy, called the Lockman Hole. In those galaxies that glow most brightly in the infrared, astronomers suspect that frantic star formation is in progress, in episodes called starbursts. In nearer galaxies, ISO's astronomers can relate strong infrared emissions to collisions and violent eruptions in galactic cores, which have punctuated the evolution of the galaxies.

The farthest known galaxy observed by ISO is a quasar called BR 1202-0725, dating from a time when the Universe was less than one tenth of its present age. Already it is dusty, indicating that star birth and death had ocurred by this early stage.

"The disks tell us that the system at least made small bodies, so it is likely that it also made planets," said Harm Habing of Leiden University in the Netherlands. "Our statistical study reveals that 50 percent of all young stars have these debris disks. ISO is breaking the ground for projects that will go in search of planets, even Earth-like planets, in the far future."